Materials & Prep
- Display the class map of earthquakes and volcanoes.
- Copy the four evidence cards and the three boundary scenario cards included in this lesson.
- Prepare a half-sheet exit ticket for each student.
- Draw three columns on the board labeled Divergent, Convergent, and Transform.
- No hands-on safety procedure is needed for this lesson.
Opening
DisplayShow the class map of earthquakes and volcanoes without naming the lines students previously labeled.
Ask“Why are earthquakes and volcanoes concentrated in long, narrow patterns instead of being spread evenly across Earth? What could be moving or interacting to create those patterns?” Students commit to an explanation in two sentences or with a labeled sketch. They must include what they think causes the pattern, not only where the pattern is.
ConnectHave students quickly recall that earthquakes are sudden releases of energy in Earth’s crust and volcanoes form when magma reaches the surface. Ask, “What evidence on this map is an observation, and what part of your answer is an inference?” Take two responses and record one observation and one inference.
Build the Explanation
ExplainContinents move because they are attached to large pieces of Earth’s rigid outer layer called tectonic plates. The plates move slowly over the softer, moving material beneath them. The map pattern is not caused simply by continents moving randomly. Most earthquakes and volcanoes occur where plates interact, because plate motion builds stress, causes rocks to break, or allows magma to rise.
DisplayGive students these evidence cards. For each card, students mark O for an observation and I for the inference it supports.
Evidence Card 1: The coast of eastern South America has a shape that roughly matches the coast of western Africa, as if the continents could fit together.
Evidence Card 2: The same Mesosaurus fossil is found in rocks in eastern South America and southern Africa. Mesosaurus was a freshwater reptile that could not have crossed the Atlantic Ocean.
Evidence Card 3: Rock layers of the same age and type continue from eastern South America into western Africa when the continents are placed together.
Evidence Card 4: Scratches and deposits made by ancient glaciers are found in southern Africa, South America, India, Australia, and Antarctica. Their directions make more sense when the continents are placed together near the South Pole.
Think aloud“The matching coastlines are an observation. I should not claim that the continents definitely moved from that observation alone. The matching fossils and rocks provide separate evidence. When several independent observations fit the same explanation, the explanation that the continents were once joined and later moved becomes stronger.”
MisconceptionStudents may say the matching coastlines prove the continents drifted because the continents floated through the ocean. Clarify that continents do not move independently through ocean water. They are carried as part of tectonic plates.
Guided Map Reasoning
ModelUse the class map to connect plate motion to the pattern. At a boundary, ask three questions in order: Where is the pattern? What direction are the plates moving? What process would that motion cause?
DisplayAdd these descriptions to the three board columns.
Divergent boundary: Two plates move apart. Magma rises and cools to form new crust. Expect many shallow earthquakes and volcanic activity, often along a ridge or rift.
Convergent boundary: Two plates move toward each other. One plate may sink beneath the other, or two continents may collide. Expect earthquakes; subduction commonly produces volcanoes, trenches, and mountains, while continent-continent collision produces large mountains and earthquakes.
Transform boundary: Two plates slide past each other horizontally. Stress builds and is released as earthquakes. Volcanic activity is not usually produced along the boundary because neither plate is being pulled apart or forced down into the mantle.
ComparePoint to an earthquake and volcano pattern on the map. Ask, “What does the pattern show us directly, and what must we infer about plate motion?” Then point to a long earthquake pattern with few volcanoes. Ask, “Which boundary type could explain this pattern, and why?”
Check for understandingStudents hold up D, C, or T for each description: “Plates move apart and new crust forms.” “An oceanic plate sinks beneath a continental plate.” “Plates slide past one another and earthquakes occur, but volcanoes are uncommon.” Require students to add the cause to one answer using the stem, “This pattern occurs because .” Correct the common answer “convergent means volcanoes” by emphasizing that subduction, not convergence alone, produces the magma that feeds many volcanoes.
Independent CER Task
StudentsComplete both parts independently, then compare answers with a partner. Use the map and evidence cards as evidence.
Part 1: Write a claim explaining whether continents have moved. Support the claim with two different observations from the evidence cards. For each observation, explain why it supports the claim.
Part 2: Classify each scenario as divergent, convergent, or transform. Describe the plate motion and predict the main evidence scientists would observe.
Scenario A: Two plates are moving away from each other. The boundary has a long ridge, shallow earthquakes, and lava that cools to form new crust.
Scenario B: A dense oceanic plate is moving toward a continental plate and sinking beneath it. The boundary has a deep trench, frequent earthquakes, and a chain of volcanoes on the continent.
Scenario C: Two plates are moving horizontally in opposite directions along the same boundary. The boundary has frequent earthquakes but no long chain of volcanoes.
ScaffoldProvide this organizer for students who need a defined entry point: “My claim is . Evidence 1 is . This supports my claim because . Evidence 2 is . This supports my claim because . Scenario __ is a boundary because the plates . I predict because .” Students may draw arrows for plate motion before writing.
CirculateLook for students who only label a boundary. Prompt them to complete the causal chain: “The plates move . That motion causes . That produces the earthquakes, volcanoes, mountains, or new crust we observe.”
ExtensionStudents explain why a transform boundary can produce many earthquakes without producing a long line of volcanoes, using the idea of stress release and the absence of subduction or seafloor spreading.
Closing Check
Exit ticketStudents answer all three prompts without using the board:
- Give two observations that support the claim that continents have moved, and explain how each supports the claim.
- Describe what happens at a convergent boundary where an oceanic plate meets a continental plate. Include the direction of motion and two expected results.
- A boundary has many earthquakes, plates sliding sideways, and few volcanoes. Identify the boundary type and explain why the pattern fits.
ExpectedA complete response connects evidence to the claim rather than merely naming a location. For the boundary questions, students should describe motion, process, and resulting evidence.